The invention relates to an outside rear view mirror for motor vehicles having an adjustably supported glass subassembly and an electric adjusting mechanism for remote-controlled adjustment of the glass subassembly, wherein the position of the glass subassembly, in particular the angular position, is determinable by means of at least one sensor.
Outside rear view mirrors of the type described above are known from prior art. Such outside rear view mirrors comprise an adjusting mechanism for adjusting the mirror glass, which is provided on the glass subassembly. The driver is therefore able by remote control to adapt the glass subassembly of the outside rear view mirror to his individual requirements. More prestigious vehicles have a so-called memory function. For such memory function specific settings, e.g. of the driver""s seat and in particular also of the outside rear view mirrors, are stored so that, after a change of driver, the memory function merely has to be tripped for the seat and/or the outside rear view mirrors to be brought into the correct setting for the driver. For such functions, the position of the glass subassembly has to be detectable by means of a sensor in order to store the various setting values for the various drivers after the initial start-up and enable start-up upon subsequent tripping of the memory function.
From prior art so-called memory potentiometers are known, which are fitted in outside rear view mirrors as sensors for determining the position of the glass subassembly. Depending on the position of the glass subassembly, corresponding voltage output values associated with an angular position arise at the memory potentiometer. For this purpose, the potentiometers fitted e.g. in the glass adjusting mechanisms are supplied with an input voltage of e.g. 5 V DC. Depending on the position of the glass subassembly, an output voltage of between 5% and 95% of the applied input voltage may then be tapped at the memory potentiometers. From the voltage drop between input voltage and output voltage it is to therefore possible to derive the position of the glass subassembly.
The drawback of the known sensors for determining the position of the glass subassembly in an outside rear view mirror is that their functioning may be impaired by corrosion. As soon as water, especially combined with salt, penetrates the outside mirror, the sensitive resistive lines or sliders of the memory potentiometers may become damaged and therefore cause failures of the memory function.
The object of the present invention is to provide an outside rear view mirror, in which the position of the glass subassembly is determinable by means of a sensor which is insensitive to corrosion.
This object is achieved by an outside rear view mirror having an adjustably supported glass subassembly and an electric adjusting mechanism for remote-controlled adjustment of the glass subassembly, wherein the position of the glass subassembly, in particular the angular position, is determinable by means of at least one sensor. The sensor is designed in the manner of a magnetic sensor, which cooperates in such a way with a magnetic element provided in the outside rear view mirror that the magnetic sensor or the magnetic element participates in the adjusting motion of the glass subassembly and the magnetic sensor in dependence upon the position of the magnetic element supplies a variable output signal, from which in an evaluation unit the position of the glass subassembly is derivable.
The invention is based on the fundamental idea of using a sensor which operates without contact to determine the position of the glass subassembly. It has in such case proved a particularly suitable operating principle to use the variation of the magnetic field strength as a function of the arrangement of a measuring point in a magnetic field to measure the position of the glass subassembly in the agreed manner.
According to the invention it is therefore proposed to design the sensor in the manner of a magnetic sensor, which in the outside rear view mirror cooperates with a magnetic element, i.e. a component surrounded by a magnetic field, e.g. a permanent magnet, in such a way that the magnetic sensor or the magnetic element participates in the adjusting motion of the glass subassembly, with the result that the adjustment of the glass subassembly gives rise to a relative movement between magnetic sensor and magnetic element. The magnetic sensor is consequently moved in the magnetic field of the magnetic element and is therefore exposed, depending on the position of the glass subassembly, to different field intensities in the magnetic field of the magnetic element. Depending on the respective field intensity the magnetic sensor supplies a variable output signal, wherein a specific position of the glass subassembly is associated with the output signal so that by evaluation of the output signal in an evaluation unit the position of the glass subassembly is derivable. Thus, a reliable sensor is available for non-contact measurement of the position of the glass subassembly. In principle, it is of no importance to the function of the invention whether the magnetic sensor or the magnetic element participates in the adjusting motion of the glass subassembly. As in many cases it will admittedly be easier to arrange the magnetic sensor in a fixed manner and the magnetic element in a movable manner, the following description is based on this type of arrangement. The reverse arrangement is however likewise realizable without difficulty.
The magnetic sensor may, in principle, be of any desired design so long as it generates an output signal which varies with the change of position of the magnetic element in the magnetic field. For example, the use of GMR sensors, magnetoresistors or magnetoresistive sensors is conceivable. Particularly suitable are so-called Hall-effect sensors because said type of sensor is already commercially available at low cost together with correspondingly suitable magnetic elements, e.g. permanent magnets obtained by vacuum melting. Hall-effect sensors present good spatial resolution even with low positioning motion amplitudes.
In order to evaluate the output signal of the magnetic sensor, the output signal has to be relayed to an evaluation unit, e.g. the central processing unit in a motor vehicle. In order to guarantee reliable signal transfer even in the event of extended conductor paths, it is advantageous for the output signal to have a relatively high voltage level. It is therefore to advantageous to integrate a signal amplifying circuit in the magnetic sensor so that the output signals may be proportionally boosted. It is further advantageous for the magnetic sensor to comprise a temperature compensating circuit so that the measurement result is not corrupted by temperature influences.
It is particularly advantageous when the magnetic sensor may be supplied with a supply voltage of around 5 V DC as said supply voltage has also already been used previously for supplying the known sensors, so that there is no need to adapt the supply voltage to the new magnetic sensors. However, in principle any other supply voltage is also conceivable so long as it may be made available in the vehicle.
It is furthermore advantageous when the magnetic sensor in dependence upon the position of the magnetic element produces an output voltage in the voltage range of 5% to 95% of the supply voltage because said voltage range likewise corresponds to the previously used voltage range, with the result that the previously used evaluation units may continue to be used substantially without modification. However, in principle any other voltage range is also conceivable so long as it enables an adequate accuracy of the measuring signals over the positioning range.
In principle, the use of any magnetic element which builds up a magnetic field is conceivable in the outside rear view mirror according to the invention. For example, it is also possible to use magnetic elements, in which a magnetic field is generated by the flux of a specific electric current. Particularly inexpensive are magnetic elements designed in the manner of permanent magnets. Permanent magnets are also advantageous because they do not have to be supplied with energy from outside and are therefore extremely reliable. In the present case, use should be made of permanent magnets having magnetic properties, which at any rate vary only slightly within the average life of a motor vehicle.
Particularly suitable for use in the outside rear view mirror according to the invention are magnetic elements which as a whole have a bar-shaped geometry, wherein the north and south poles of the magnetic element are disposed one at either end of the magnetic bar.
For generating magnetic fields having specific advantageous properties, it is advantageous when the magnetic element is composed of a plurality of magnetic sub-elements. By purposeful combination of various of the latter, which may present e.g. different magnetic properties and/or different orientations, it is possible to generate a magnetic field which may be evaluated particularly well by the magnetic sensor. Said type of composition of the magnetic element from a plurality of magnetic sub elements is particularly advantageous in the case of lower piece numbers where manufacture of a one-piece magnetic element, the properties of which are specified for the special rear view mirror, is uneconomical because of the fixed-cost component. For larger-series production it is however naturally also possible for a correspondingly specified magnetic element, e.g. a permanent magnet, to be formed from one piece and magnetized in accordance with the required magnetic properties.
The combination of magnetic sensors with magnetic elements for determining a relative position between magnetic sensor and magnetic element may be operated in various known operating modes. For example, the unipolar head-on operating mode is known, whereby the one pole of a permanent magnet is moved up to the magnetic sensor head-on. In said case, however, the output signal of the magnetic sensor does not vary linearly with the distance of the magnetic pole from the magnetic sensor. Rather, the output signal, as the distance of the magnetic pole from the magnetic sensor increases, asymptotically approaches the zero point so that at least in said measuring range there is poor resolution of the positioning motion with said operating mode.
Also known is the unipolar slide-by operating mode, whereby the one pole of a permanent magnet lies at a specific distance opposite the magnetic sensor and during the positioning motion is conveyed past the magnetic sensor parallel to the magnetic sensor at a constant distance y. With said operating mode, the output signal reaches a maximum as soon as the permanent magnet lies directly opposite the magnetic sensor. In the positioning range of the permanent magnet, starting from said position with a maximum output signal, the output signal does not vary linearly but drops underproportionally slightly. As a result, in the positioning range around the maximum of the output signal no good resolution of the positioning motion is possible with said operating mode either.
Particularly suitable for the purpose according to the invention is the bipolar slide-by operating mode. With said operating mode, use is made of a magnetic element comprising at least two magnetic portions, e.g. two magnetic sub-elements. As with the unipolar slide-by operating mode, the magnetic element is disposed at a specific distance y opposite the magnetic sensor and then during measurement is displaced at a constant distance y parallel to the magnetic sensor. With the bipolar slide-by operating mode, the output signal assumes the reference value for the zero position as soon as the magnetic element lies at the shortest possible distance opposite the magnetic sensor. From this point the output signal rises linearly in the one direction or drops linearly in the opposite direction. The gradient of the linear measuring signal range may in said case be influenced by the distance between the two portions of the magnetic element of reverse polarity. The greater the distance between the two portions, the lower the gradient of the measuring signal in the linear measuring range.
Given the use of a magnetic sensor with associated magnetic element in the bipolar slide-by operating mode, the measuring range of the magnetic to sensor is selected in just such a way that the positioning motion of the glass subassembly to be measured falls precisely in the linear range of the output signal shape. The effect is thereby achieved that the positioning motion may be imaged with substantially the same resolution over the entire positioning range.
In principle, it does not matter whether the magnetic sensor or the magnetic element participates in the adjusting motion of the glass subassembly because for determination of the position of the glass subassembly it is immaterial whether the magnetic sensor moves relative to the magnetic element or the magnetic element moves relative to the magnetic sensor. It is however advantageous when the magnetic sensor is disposed in a fixed manner on a basic body of the outside rear view mirror, e.g. an amplifier plate, and the magnetic element participates in the adjusting motion of the glass subassembly. For, should damage be caused to the outside rear view mirror by external influences such as an accident, in most cases only the glass subassembly and the adjusting mechanism are damaged to such an extent as to require replacement. By virtue of the fixed arrangement of the magnetic sensor it is therefore possible in most cases to avoid the need to replace the magnetic sensor following damage to the outside rear view mirror. Admittedly, in most cases the magnetic element will have to be replaced instead but this involves considerably less expense because of the lower component price for the magnetic element and the lower assembly outlay, especially in the case of permanent magnets which do not require cabling.
When the combination of magnetic sensor and magnetic element is operated in the bipolar slide-by operating mode, it is, as described, necessary for the magnetic element to be displaced at a substantially constant distance parallel to the magnetic sensor. Given the fixed arrangement of the magnetic sensor on a basic body, it is therefore advantageous when the basic body in the region of the magnetic sensors has indentations or recesses, into which the magnetic element may penetrate to a differing depth in dependence upon the position of the glass subassembly. When the magnetic sensor is disposed on a printed-circuit board or the like which is in turn fastened to the basic body, the printed-circuit board also has to have correspondingly arranged recesses so that it may be penetrated by the magnetic elements. In other words, the magnetic sensor may be disposed at a specific height on or in the basic body and by virtue of the indentation or recess in the basic body the magnetic element has sufficient margin for it to be displaced over the entire positioning range parallel to the magnetic sensor. By virtue of the geometry of the indentation or recess, moreover, guidance of the magnetic element relative to the magnetic sensor may be achieved. This is possible e.g. by virtue of the recess having an only slightly larger diameter than the magnetic element.
Especially given operation of the magnetic sensor in the bipolar slide-by operating mode, the magnetic element has to be arranged so as to be displaceable at a substantially constant distance y parallel to the magnetic sensor during the adjusting motion of the glass subassembly.
To enable accommodation of the measuring system according to the invention in the smallest possible installation space, it is advantageous for the magnetic element to be integrated in the adjusting mechanism.
It is therefore particularly advantageous in cases where the adjusting mechanism comprises a gear element, in particular a gear rack or worm plunger, by means of which a positioning motion is transmissible to the glass subassembly, to design and dispose the magnetic element in such a way that it participates in the positioning motion of the gear element. Each time a positioning motion is transmitted by the gear element the magnetic element is carried along, so that by said means the adjustment of the glass subassembly may be indirectly measured. With each position of the gear element, as a rule, one position of the glass subassembly is clearly associated. For realizing said operating principle it is, for example, conceivable to fasten the magnetic element to the end of the gear element, in particular to the end of a gear rack or to the end of a worm plunger. Thus, by simple means it becomes possible to use already serially employed adjusting mechanisms for the sensor system according to the invention simply by adding the magnetic element onto the existing gear element.
Given the use of permanent magnets made of metal materials, e.g. iron, as a magnetic element, it is necessary to rule out corrosion of the permanent magnet for the long term because the magnetic properties of the magnetic element would vary as a result of corrosion, with the result that reliable operation of the sensor system according to the invention would not be guaranteed under all circumstances. In a particularly advantageous manner the corrosion protection of the magnetic element may be guaranteed when, for manufacture of the gear element used in the adjusting mechanism to transmit a positioning motion to the glass subassembly, a magnetic element, preferably a permanent magnet, is extrusion-coated with plastics material. Such measure guarantees reliable corrosion protection of the magnetic element because the entire surface of the magnetic element is enveloped in plastics material. Furthermore, the spatial requirement of the magnetic element may be substantially eliminated because it is fully integrated in the gear element, which is to be provided in any case. In terms of methodology, such gear elements with an embedded magnetic element may be manufactured, e.g. by insert molding. The end result is a multi-functional part which may be used simultaneously as a magnetic element and a gear element.
An even more advantageous possibility of manufacturing a gear element with an integrated magnetic element is when the gear element is creatively formed using a magnetizable material. For example, the gear element may be die-cast from a magnetizable metal material. It is even more advantageous, however, when the gear element is manufactured by injection molding using a plastics material, which contains a plastic bound magnetic material. The end result is therefore a gear element made of plastics material having the known advantages of plastics material, such as, e.g. low weight and high wear resistance, which at the same time, because it contains magnetic material, e.g. neodymium-iron-boron, is magnetizable in such a way as to be usable as a permanent-magnet magnetic element. As such materials are processable by injection molding, they are also inexpensive to manufacture. After shaping, e.g. by injection molding, the finished gear elements are magnetized in a defined manner.
In many cases considerable demands are placed upon the gear element, e.g. a gear rack or worm plunger, in terms of mechanical stability and wear resistance. Said demands may occasionally be met only with difficulty by plastics materials containing plastic-bound magnetic materials. It is therefore advantageous when the gear element is manufactured in a multicomponent injection molding process, whereby a plastics material containing a plastic-bound magnetic material is extrusion-coated with another plastics material. This allows the core of the gear element to be manufactured from magnetizable material, while the outer regions of the gear element may be manufactured from a highly stable and/or wear-resistant plastics material.
For contacting of the magnetic sensor, it is advantageous to use printed conductors which are extrusion-coated with plastics material, in the manner described, e.g. in DE 198 41 551. The electric lines used for contacting the magnetic sensors may be provided, e.g. by insert molding in an amplifier plate. It is also conceivable to design the printed conductors as a pressed screen or lead frame, on which the magnetic sensor is contacted and then together with the pressed screen extrusion-coated with plastics material. Also conceivable is the use of multicomponent injection molding processes for manufacturing the amplifier plate with partial metal-plating of plastic components for producing printed conductors or foil-type printed-circuit boards, rigid printed-circuit boards or conventional circular conductors.
As with the sensor system according to the invention position measurement is effected without contact, the magnetic sensor as a protection against corrosion may be extrusion-coated with plastics material or encapsulated in a sealing compound, in particular silicone. Alternatively, the magnetic sensor as a protection against corrosion may be disposed in a sealable dry chamber of the outside rear view mirror, such as is described e.g. in DE 199 28 384.
For application of the measuring principle according to the invention in most outside rear view mirrors it is necessary to provide two magnetic sensors and two magnetic elements disposed in a functionally complementary manner thereto. Each combination of magnetic sensor and magnetic element then measures the angular position of the glass subassembly relative to a respective swivelling axis.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.